5 mil hood?? seems pretty thick, thought you could only get those on diving suits. Your neck might get pretty sore from wearing that. With 3 mil boots and gloves you could go in now on a warmer day and be alright for maybe an hour, depends on your cold tolerance. By mid to late april you should be pretty comfortable in all of that.
Watch the Islip buoy water temps. Going in water below 48 will be painful. I surfed with a longboarder last weekend who wore 3mm boots and he didn't last half an hour.
Mid/Late April sounds about right.